1. Field of the Invention
The present invention relates to portable monitoring devices. The invention further relates to portable monitoring devices comprising a hearing aid and comprising an EEG monitoring system for monitoring biological incidences. The invention more specifically relates to portable monitoring devices comprising a housing, at least one microphone for receiving ambient sound, acoustic signal processing means for processing a signal from the microphone, and an output transducer. The invention also relates to a method of monitoring an EEG signal.
In general the prevalence of hearing aid use is more profound in the population of elderly persons than in the general population.
Also the prevalence of diabetes is more profound in the elderly population, and it has been realized that there is a significant group of hearing aid users with diabetes.
For persons with diabetes, detailed control of blood sugar concentration is important. The level should not be too high in order to limit the risk of long term effects of diabetes. The blood sugar level should also not be too low, since this might lead to hypoglycemia, where the person becomes absent and may become unconscious. Hypoglycemia may be fatal. Therefore, persons with diabetes often need to measure their blood sugar level on a daily basis, or several times a day, by testing a small blood sample. Some persons with diabetes have the problem that they will not feel any warning before the blood sugar concentration has fallen to a level where hypoglycemia occurs. However, characteristic changes in the electroencephalographic (EEG) signals of a person with diabetes will be seen before the onset of hypoglycemia.
Also for persons with epilepsy, characteristic changes in the EEG signals may be seen before the onset of an attack.
2. The Prior Art
It is known from WO-A1-2006/066577 to apply a system measuring EEG signals continuously on a person, for detecting if a person with diabetes is getting close to a hypoglycemic event.
WO-A2-2007/144307 presents an algorithm for detecting hypoglycemia from an EEG signal.
In U.S. Pat. No. 6,572,542 both the EEG signal and an Electrocardiography (ECG) signal are applied for detection of hypoglycemia.
Such systems have been developed to a level where they can be carried continuously by a person without limiting the person in daily activities. If the onset of hypoglycemia is detected, e.g. according to a method described in WO-A2-2007/144307, the person is alerted by the system and is instructed to either measure the blood sugar concentration or to drink or eat something increasing the blood sugar concentration. Often a surgical operation is needed in order to arrange electrodes subcutaneously on the head. These electrodes will, in some way, be connected with an electronic device arranged on the body.
For many hearing impaired persons using a hearing aid, it may be difficult to handle this small high tech product. This may especially be a problem to elderly persons. If these persons are equipped with an EEG monitoring system, which also needs correct handling in order to function properly, the risk of incorrect handling of at least one of these two devices will most likely increase significantly. This imposes a risk of missing an alarm of an upcoming biological incidence, such as hypoglycemia, or of not having the possible optimal hearing.
Therefore, it will often be a problem to equip elderly persons with both a hearing aid and an EEG monitoring system, both being equipment to which they must pay attention and handle in specific different ways in order to obtain the benefits of these devices. Also, more devices arranged on the body of a person increase the risk of overlooking one. Further, a hearing aid user often needs two hearing aids.